Solid State Lamp Using Light Emitting Strips

ABSTRACT

In one embodiment, an LED lamp has a generally bulb shape. The LEDs are low power types and are encapsulated in thin, narrow, flexible strips. The LEDs are connected in series in the strips to drop a desired voltage. The strips are affixed to the outer surface of a bulb form to provide structure to the lamp. The strips are connected in parallel to a power supply, which may be housed in the lamp. Since many low power LEDs are used and are spread out over a large surface area, there is no need for a large metal heat sink. Further, the light emission is similar to that of an incandescent bulb. In other embodiment, there is no bulb form and the strips are bendable to have a variety of shapes. In another embodiment, a light sheet is bent to provide 360° of light emission. Many other embodiments are described.

CLAIM OF PRIORITY

This application is a continuation application and claims priority under35 U.S.C. § 120 to U.S. application Ser. No. 16/833,290, filed Mar. 37,2020, which is a continuation of U.S. application Ser. No. 16/380,858,filed Apr. 10, 2019, which is a continuation of U.S. application Ser.No. 15/417,037, filed Jan. 26, 2017, which is a continuation of U.S.application Ser. No. 14/929,147, filed Oct. 30, 2015, which is acontinuation of U.S. application Ser. No. 14/334,067, filed Jul. 17,2014, which is a continuation of U.S. application Ser. No. 13/681,099,filed Nov. 19, 2012, which is a continuation of U.S. application Ser.No. 13/032,502, filed Feb. 22, 2011, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a solid state lamp, such as a lamp using lightemitting diodes (LEDs), and, in particular, to a solid state lamp thatrequires relatively little cooling.

BACKGROUND

A huge market for LEDs is in replacement lamps for standard, screw-inincandescent light bulbs, commonly referred to as A19 bulbs, or lessformally, A-lamps. The letter “A” refers to the general shape of thebulb, including its base, and the number 19 refers to the maximumdiameter of the bulb in eighths of an inch (e.g., 2⅜″ diameter). Such aform factor is also specified in ANSI C78-20-2003. Therefore, it isdesirable to provide an LED lamp that has the same screw-in base as astandard light bulb and approximately the same size diameter or less.Additional markets exist for replacing other types of standardincandescent bulbs with longer lasting and more energy efficient solidstate lamps.

Typical LED lamps having an A-shape use high power LEDs in order to useas few LEDs as possible to achieve the desired lumen output (e.g.,600-1000 lumens). Such LEDs may each draw a current greater than 300 mAand dissipate 1 W or more. Since the LED dies are on the order of about1 mm², adequate heat removal is difficult because the heat is usuallyhighly concentrated within a small surface area and often located nearthe base of the lamp where it shares heat dissipation capacity with thepower supply electronics. The high power LED junction temperaturesshould be kept under 125° C. to ensure the LEDs remain efficient andhave a long life. A common design is to mount high power LEDs on a flat,heat conductive substrate and provide a diffusive bulb-shaped envelopearound the substrate. The power supply is in the body of the lamp.Removing heat from such designs, using ambient air currents, isdifficult since the lamp may be mounted in any orientation. Metal finsor heavy metal heat sinks are common ways to remove heat from suchlamps, but such heat sinks add significant cost and have otherdrawbacks. It is common for such LED replacement lamps to cost $30-$60.Additionally, the light emission produced by such a solid state bulb isunlike that of an incandescent bulb since all the LEDs are mounted on arelatively small flat substrate. This departure from the standardspherical distribution patterns for conventional lamps that are replacedwith LED replacement lamps is of particularly concern to the industryand end users, since their existing luminaires are often adapted tospherical light emission patterns. When presented with the typical“hemi-spherical” type emission from many standard LED replacement lamps,there are often annoying shadow lines in shades and strong variations inup/down flux ratios which can affect the proper photometricdistributions.

What is needed is a new approach for a solid state lamp that replaces avariety of standard incandescent lamps, using standard electricalconnectors and supply voltages, where removing adequate heat does notrequire significant cost or added weight and where other drawbacks ofprior art solid state lamps are overcome.

SUMMARY

In one embodiment, a solid state lamp has a generally bulb shape, suchas a standard A19 shape. Many other form factors are envisioned.

The light source comprises an array of flexible LED strips, where eachstrip encapsulates a string of low power (e.g., 20 mA), bare LED dieswithout wire bonds. The strips are affixed to the outside of a bulbform, which may be clear plastic, a metal mesh, or other suitablematerial. The strips are thin, allowing heat to be transferred throughthe surface of the strips to ambient air. An optional thin protectivelayer over the strips would also transmit heat to the ambient air.Further, the strips are spaced apart from each other to expose the bulbform to ambient air, allowing heat absorbed by the underlying bulb formto be dissipated. Therefore, there is a low heat-producing large surfacearea contacted by ambient air. There may be openings in the bulb formfor air circulation within the bulb form. The strips can be bent toaccommodate any form factor, such as an A-shape bulb.

In one embodiment, the strips are only a few millimeters wide and arearranged extending from the lamp's base to the apex of the bulb form.

In another embodiment, the strips are affixed around the perimeter ofthe bulb form either in a spiral pattern or with parallel strips. Otherpatterns of the strips are envisioned.

In one embodiment, to replace a 60 W incandescent bulb, there are 12 LEDstrips affixed to a bulb form, each strip having 12 LEDs in series forgenerating a total of 800-900 lumens. The 12 strips are driven inparallel. The LEDs may be driven at a low current so as to generate verylittle heat, and are spread out over a relatively large bulb surface,enabling efficient cooling by ambient air. By driving the LEDs at lowerlocalized current density, it is also possible to significantly enhancethe overall efficacy of the LED by as much as 30% which deliverssignificant energy savings when compared to the large LED chip typelamps that are in the market.

By using unpackaged LED dies in the strips, and using traces in thestrips to connect the dies in series, the cost of each strip is verylow. Using bare LED dies in the strips, compared to packaged LEDs,reduces the cost per LED by 90% or more, since packaging of LED chips tomount them in a sealed surface mount package is by far the largestcontributor to an LED's cost.

White light may be created by using blue LEDs in conjunction with aphosphor or combinations of phosphors or other light convertingmaterials in either proximate or remote configurations. Light emittingdies other than LEDs may also be used, such as laser diodes.

Many other lamp structures are envisioned. For example, the strips mayhave sufficient mechanical integrity to not require being affixed to arigid form. In one embodiment, a plurality of strips extends from a baseand the strips are bendable by the user to have any shape and to producea customized light emission pattern. In another embodiment, a flexibletransparent substrate encapsulating the light emitting dies is formed asa sheet and is bent to form a cylinder or other shape to replace astandard incandescent light bulb.

In another embodiment, the solid state lamp is compressible for storageor shipping and expandable to various heights and configurations by theuser.

To provide a consistent overall color temperature using LEDs from avariety of bins, the strips may be tested for color temperature andcombined in a single lamp to achieve the desired overall colortemperature when the light output from the plurality of strips ismerged.

Dynamic feedback is used in one embodiment to energize redundant stripsin the event another strip has failed. The currents through the variousstrips may be detected to determine that a strip has failed. In arelated embodiment, the currents are monitored to determine an increasein current, indicating that one or more LEDs in the strip are becomingtoo hot and are drawing more current. The heated strips are thencontrolled to have a reduced duty cycle to cool them, while the dutycycle of one or more other strips is increased to offset the reductionin flux.

Many other embodiments are described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is side view of a solid state lamp, using a plurality of LEDstrips, in accordance with one embodiment of the invention.

FIG. 2 illustrates the internal AC/DC power supply and the positive andnegative terminals for the strips.

FIG. 3 is a top down view of FIG. 1 illustrating the connections of allthe strips to the positive DC terminal.

FIG. 4 is a schematic diagram showing the plurality of LED stripsconnected in parallel.

FIG. 5 illustrates how the LEDs can have different densities to providemore uniform light output over the surface of the bulb form or to bettermimic the light emission pattern of conventional light sources.

FIG. 6 illustrates the LED strips being latitudinally arranged parallelto one another, with a reduced pitch near the middle of the bulb toachieve a more uniform density of LEDs.

FIG. 7 illustrates a cylindrical bulb that has more uniform light outputusing identical LED strips.

FIG. 8 is a perspective view of a solid state lamp having flat sides.

FIG. 9A is a perspective view of a portion of an LED strip that can beused in the various lamps. All strips described herein can instead beformed as sheets of encapsulated bare LEDs connected in combinations ofserial and parallel.

FIG. 9B illustrates the LED strip of FIG. 9A where the substrateconductors terminate at only one end of the strip.

FIG. 10A is a cross-sectional view of a portion of an LED strip orsheet, where the LEDs are connected in series.

FIG. 10B is a magnified top down view of FIG. 9A showing how the LEDsare connected in series by conducting traces on the substratessandwiching the bare LEDs.

FIG. 11A is a cross-sectional view of the end of an LED strip or sheetshowing how the metal leads of the strip or sheet can be exposed forattachment to a power supply terminal.

FIG. 11B is a top down view of the end of the LED strip or sheet of FIG.10A showing a termination pad of the strip.

FIG. 12 is a cross-sectional view of a portion of another embodiment LEDstrip or sheet, where the LEDs are connected in series via a conductivelink.

FIG. 13 is a cross-sectional view of a portion of an LED strip or sheetwhere light is bidirectionally emitted.

FIG. 14 is a cross-sectional view of a portion of another embodiment ofan LED strip or sheet where light is bidirectionally emitted.

FIG. 15 is a cross-sectional view of a portion of yet another embodimentof an LED strip or sheet where light is bidirectionally emitted.

FIG. 16 is a front view of a light sheet containing many encapsulatedbare LEDs. The light sheet may be bidirectional or emit from only oneside.

FIG. 17 illustrates the light sheet of FIG. 16 bent in a cylinder as areplacement for an incandescent bulb.

FIG. 18 illustrates the light sheet of FIG. 16 bent in a cone ortruncated cone as a replacement for an incandescent bulb.

FIG. 19 illustrates a plurality of LED strips around a form, where thecolor temperatures of the individual strips are combined to create anoverall target color temperature.

FIG. 20 illustrates a solid state lamp formed by a corrugated LED sheetor by a plurality of LED strips affixed to a form, where the lamp may becompressible.

FIG. 21A illustrates a solid state lamp where the LED strips arebendable to create a custom light emission pattern.

FIG. 21B illustrates a solid state lamp where the LED strips broadennear the “light center” of the lamp and concentrate more light emission.

FIG. 22 is similar to FIG. 21A, where the LED strips are straight butcould be fixed or able to be bent at various angles.

FIG. 23A illustrates a solid state lamp formed of a single LED sheet ora plurality of LED strips, where the sheet or strips are configured tocreate a polygonal cross-section.

FIG. 23B is a cross-sectional view of FIG. 23A along line A-A in FIG.23A.

FIG. 24 illustrates a solid state lamp, similar to FIG. 23A, with adiffuser being positioned over it.

FIG. 25 illustrates a solid state lamp, similar to FIG. 23A, with areflector surrounding the LEDs.

FIG. 26A illustrates a solid state lamp having a plurality of bendableLED strips supported at their ends to form a lamp having a customizableshape.

FIG. 26B is a top down view of FIG. 26A.

FIG. 27 illustrates a solid state lamp that is compressible forpackaging.

FIG. 28 is a bisected view of FIG. 27 in its compressed state, with thescrew-in type electrical connector in its stored position.

FIG. 29A is a perspective view of the electrical connector of FIG. 28 inits down position.

FIG. 29B is a top down view of the electrical connector of FIG. 29A.

FIG. 29C is a cross-sectional view of a push-in connector for anEdison-type screw-in socket.

FIG. 30 illustrates an electrical connector affixed to a handle toprovide torque for screwing a solid state lamp into a socket.

FIG. 31 is a side view of a solid state lamp that has a directed lightemission.

FIG. 32 is a top down view of the lamp of FIG. 31 where the LED stripsare arranged radially on a support surface.

FIG. 33 is a top down view of the lamp of FIG. 31 where each LED striphas a curved shape.

FIG. 34A illustrates an extended, self-supporting light strip that maybe rolled up.

FIG. 34B illustrates the light strip of FIG. 34A rolled up.

FIG. 35 illustrates a telescoping lamp formed of concentric, cylindricallight sheets.

FIG. 36 illustrates a lamp formed of a spiraling light strip.

FIG. 37A illustrates a cylindrical lamp formed of a light sheet, wherethe LEDs are facing inward.

FIG. 37B illustrates a truncated cone lamp formed of a light sheet,where the LEDs are facing inward.

FIG. 38 is a cross-sectional view of three overlapping lightsheets/strips for increasing light output per area and/or to permitmixing of different wavelengths.

FIG. 39 illustrates a stretchable light sheet for affixing over a form,such as a shallow dome.

FIG. 40 illustrates a circuit for automatically energizing one or moreredundant light strips when a normally energized light strip fails. FIG.40 is also used to illustrate other active controls for the LED strips.

Elements that are the same or similar in the various figures areidentified with the same numeral.

DETAILED DESCRIPTION

FIG. 1 illustrates one embodiment of a solid state lamp 10 having an A19form factor to be used as a direct replacement of conventional lightbulbs. The lamp 10 can have other form factors, such as beingsubstantially spherical.

The lamp 10 has a standard screw-in base 14. The threaded portion of thebase 14 typically contacts a neutral (or grounded) terminal of a socketconnected to a mains voltage supply. The light fixture socket providessome heat sinking for at least the internal AC/DC power supply. Thebottom terminal 16 of the base 14 contacts the “hot” terminal of thesocket. A top portion 18 of the base 14 houses at least a portion of adriver for the various LED strips 20.

The LED strips 20 will be described in further detail later. In oneembodiment, each LED strip 20 contains 12 low power LEDs 22 connected inseries so as to drop approximately 30-40 volts, depending on the type ofLEDs used. Other numbers and types of LEDs may be used.

In one embodiment, for replacing a 60 W incandescent bulb, there are 12LED strips 20, each having 12 LEDs 22 connected in series for generatinga total of 800-900 lumens. Each strip 20 extends from a connectionterminal (e.g., a common terminal or current source terminal) near thebase 14 of the lamp 10 to a top electrical termination pad 24 so theLEDs 22 are spread over the entire length of the lamp (3-4 inches frombase to apex). The 12 strips 20 are driven in parallel, parallel/series,or even variably switched by an electrical interface to the mains powerthat is contained within the lamp. Each LED 22 may be driven at therelatively low current of about 20 mA so as to generate very littleheat. Since many LEDs (e.g., 144) are spread out over a relatively largebulb surface, the heat is not concentrated, enabling efficient coolingby ambient air. Each strip 20 may be less than 5 mm wide and less than 2mm thick. In another embodiment the strips are only electricallyconnected at either the top or the bottom end, and the LEDs can bedriven in any of either series, parallel, or series and parallelconfigurations with the electrical supply terminations on either of oneor both ends or sides. The conductor terminations may occur at anylocation along the sides or even terminate at an opening along thestrip.

The strips 20 are affixed, such as with silicone or epoxy or thermalbonding, to a bulb form 30, which may be virtually any material. Sincethere may be some backscatter from the strips 20, it is preferable thatthe bulb form 30 be clear, such as molded transparent plastic, orreflective, such as reflective layer coated plastic or diffusereflecting plastic. To provide an air flow inside the bulb form 30 forremoving heat, the bulb form 30 may be provided with openings 34, whichmay be holes, slits, or other opening shapes.

In another embodiment, the bulb form is a metal mesh for improved airflow.

In another embodiment, the bulb form may be created by the length andbending radius of the strips 20 between the termination pad 24 and thedriver. This results in a lower cost lamp with increased air flow aroundall sides of the LED strips 20. It may also be advantageous to affixeach the strips 20 to a separate reinforcing backplane, which may bemade of copper or a high spring constant copper alloy such that itaffords a restorative spring force to the shape. Furthermore, theaddition of a copper backplane will also increase the coolingeffectiveness of the strips with good airflow such that fewer higherpower LED dies could be considered instead of lower power LED dies.

In another embodiment, it is known that certain types of small lampshades have a spring loaded clip designed to mechanically spring overthe lamp form and provide the mechanical connection between the bulbform and the lamp shade. In such a case, there is afforded either ametal cross-section that interfaces to the clip, or the strips areprovided with a sufficiently protective top layer that the force of themetal clip does not damage the LED dies contained within the strips.

In FIG. 1, the 12 LED strips 20 are evenly distributed around the bulbform 30, and the LEDs 22 are evenly spaced on the strips. In otherembodiments, the strips 20 are not evenly distributed, and the LEDs arenot evenly spaced to customize the light emission. If no special opticsare used, each LED 22 emits light in a nearly Lambertian pattern, so thelight from nearby LEDs gets mixed. By providing many LEDs around a bulbshape, the resulting light emission pattern is similar to that of anincandescent bulb. Since each LED die produces roughly a hemisphericaldistribution and the light merges together, the present inventioneliminates one major drawback of conventional LED replacement bulbs inthat the substantially spherical light distribution of a conventionallamp can be reproduced by the merging of the light emitted by the manysmall LEDs 22 located around the rounded bulb shape thereby moreaccurately mimicking the appearance and light distribution of a standardincandescent lamp.

FIG. 2 illustrates the inner structure of the lamp 10. A combined AC/DCconverter and current driver module 40 receives the mains voltage fromthe socket and converts the voltage to about 40 volts DC, which isgreater than the voltage drops along the strips 20. The positive voltageoutput terminal of the module 40 is connected via a wire 42 to atermination pad 24 that is mounted to the top of the bulb form 30. Themodule 40 has a common or ground terminal for connection to the otherends of the strips 20. An alternative embodiment could also have bothterminals at either end of the strip.

If the LEDs 22 are matched in terms of overall forward voltage, a singlecurrent source may be used to drive all the strips 20. The strips 20 mayalso have additional matching components or distributions of LEDscontained therein that provide for matched current flows. If the LEDs 22are not adequately matched, a separate current source and/or switchingcircuit may be used for each strip 20. The current sources and voltageconverter may be part of the same power supply module 40. The heatgenerated by the module 40 may be removed by a combination of the airopenings 34 in the bulb form 30 and the socket.

If the LEDs 22 are also not adequately matched in terms of forwardvoltage, it may be desirable to include a provision within the strips tocustom trim the performance of each strip prior to final assembly of thelamp such that they could be readily combined on a single currentsource. Means to achieve this include laser trimming of passivecomponents, fuse arrays and other such in-line manufacturing processesthat are known in the art to balance arrays of components.

FIG. 3 is a top down view of FIG. 1, illustrating the termination pad 24providing the drive voltage to each of the strips 20. The pad 24 may bea relatively large metal pad, or the pad 24 may be provided on asubstrate with metal traces connected to associated terminals or the LEDstrips 20. The wire 42 (FIG. 2) may connect to the pad 24 by a viathrough the substrate. The pad 24 may be covered with an insulator forsafety. Pad 24 may also be designed to optionally provide anelectrically insulated solid point at the top of the lamp by which tograsp the lamp and provide the torque necessary to rotate the lamp intothe socket such that the correct contact is made at the base.

FIG. 3 also illustrates an optional protective layer 46 of silicone, orother transparent layer, that protects the strips 20 and helps preventthe strips 20 from delaminating during handling by the user. This layer46 may exist over all parts of the lamp form or only over specific partsof the outer form to protect the strips 20 from mechanical damage or toprotect the user from possibly contacting the low voltage DC topterminal pad 24. The layer 46 may also provide optics, such as being adiffuser, or even contain one or more types of light convertingmaterials (e.g., phosphors) to provide conversion between blue orultraviolet emission from the dies to a broader white light output.

FIG. 4 is a schematic diagram illustrating the pad 24 providing a drivevoltage V+ to the strips 20, connected in parallel, and current sources47 connecting the other ends of the strips 20 to the common terminal ofthe driver. The current sources 47 may all be formed on one or moreintegrated circuits or formed using a combination of discrete componentsand integrated circuits. The location of the current sources 47 may beembedded within the strips or be located with other power convertingelectronics. Small power supplies for driving any number of LEDs arecommercially available or easily designed. The current through eachstring may be 20 mA in one embodiment, but depends on the types of LEDsused and other factors. The ground terminals shown at the bottom may bereferenced to ground or some other neutral reference level of theelectrical supply that enables current to flow through the string.

Since the density of LEDs 22 in FIG. 1 is less around the wider part ofthe bulb form 30 due to the larger area, the light output per area willbe less at the wider part. This may be objectionable in certainapplications. The embodiment of FIG. 5 provides a more uniform lightoutput along the length of the bulb form 30 by increasing the density ofLEDs 22 near the wider part of the bulb form 30. Thus, one of thepreferred embodiments of the lamp may closely emulate the photometric ofa standard incandescent A-lamp by virtue of a substantially uniformdensity of LEDs per unit area of the bulb form. FIG. 5 also shows thatperforations in the outer envelope may be used to induce air flowthrough the bulb for additional cooling purposes.

In another embodiment, the LEDs 22 may be affixed inside the transparentbulb form for protection of the LEDs 22.

The strips 20 may be arranged in other ways on the bulb form 30. FIG. 6illustrates the strips 20 being latitudinally arranged around the bulbform 30. The strips 20 are therefore different lengths, yet still havethe same number of LEDs 22 in them. The V+ and ground rails 50 and 52are arranged vertically to connect to the ends of the strips 20. Thepitches of the strips 20 near the wider part of the bulb form 30 may bereduced to provide an increased density of LEDs 20 near the centralregion of the bulb form 30, thereby more closely emulating a traditionallamp luminance pattern. A vertical reveal may also be provided for thatwill enable air to flow through the body of the bulb thereby providingadditional cooling.

FIG. 7 illustrates a generally cylindrical bulb form 56 that has auniform circumference for most of its length. In the industry, these areoften called “T” type lamps for their roughly tubular shape. Thisenables the strips 20 to be substantially identical and equally spacedwhile providing a uniform light output along the entire length of thelamp. Alternatively, the density of LEDs 20 could also be increased inthe central region to more closely emulate a standard filament typelamp.

In another embodiment, the strips 20 may be arranged in a spiral patternthat may even emulate the near field photometric of a conventionalcompact fluorescent lamp.

In another embodiment, there is no bulb form, and the strips 20 are heldin place by a stiff rod that runs through the center of the lamp andconnects to the ends of the strips 20. The shape (radius of curvature)of the strips 20 will be determined by the length of the rod. Such anembodiment has the greatest cooling, but the strips 20 are vulnerable tobreakage by handling by the user. A handle or other grip-able device maybe added at the top of the rod for providing the torque arm for screwingthe lamp into a socket.

In one embodiment, to greatly reduce the cost of the strips 20, the LEDs22 encapsulated in each strip 20 are bare unpackaged dies, andconductive traces in the strips 20 connect the LEDs 22 in series. Thisreduces the cost per LED 22 by 90% or more, since packaging of LED chipsto mount them in a sealed surface mount package is by far the largestcontributor to a packaged LED's cost, as shown by the most recent USDepartment of Energy SSL Manufacturing Roadmap for 2010.

FIG. 8 illustrates a solid state lamp 57 that is relatively simple tomanufacture since the support surfaces 58 for the LED strips 20 areflat. The support surfaces 58 may even be collapsible for packaging. Thesupport surfaces 58 may be transparent or reflective. If transparent,the strips 20 can be bidirectional, discussed later. By providing LEDstrips 20 on the eight sides of the support surfaces 58, 360 degrees oflight emission is obtained to emulate a bulb emission. The strips 20 areshown connected to a positive voltage V+ at one end and current sourcesin the driver module 40 at their other end. There may be more or fewersupport surfaces 58, such as three support surfaces arranged 120 degreesapart while still providing 360 degrees of light emission. Thedistribution of LEDs within the strips may be uniform or at anylocalized density as would be desired for the correct near fieldphotometric response. An LED strip 59 may be positioned on top of thelamp 57 to direct light upward for a more spherical light emission. Asimilar strip 59 can be affixed to the outer edges of the supportsurfaces 58 to emit light generally perpendicular to the LEDs on thefaces of the support surfaces. A round (e.g., cylindrical) diffuser maybe placed over the lamp 57 to provide more uniform near field emissionand allow the user to handle the lamp without damage to the LED strips20 when screwing the lamp 57 into an Edison socket. The screw-in base isnot shown in FIG. 8. The diffuser may contain air holes to allow heatedair to escape.

There may be any number of strips 20 supported by a single surface, andthe strips, being transparent, may overlap each other to increase thelight output per unit area.

In another embodiment, the shapes of the thin support surfaces 58 may bearced, such as forming a cloverleaf outline as viewed from the top down,where the LEDs are arranged on the rounded outer surface of each supportsurface to emit light around the arc. This arrangement would provide amore uniform distribution of light, similar to that of the cylindricallamp of FIG. 7. Having the LEDs arranged on thin arced sheets improvescooling since the backs of the sheets are exposed to ambient air. Anynumber of LEDs may be distributed over the arced support surface and inany relative density from uniform to highly localized.

Generally, the length of the light-emitting portion of the lamp will beon the order of 2-4 inches to take up an area the same as or less thanthe area taken up by an equivalent lumen-output incandescent lamp.

FIG. 9A is a perspective view of a portion of an LED strip 60 that maybe used as the strips 20 in all lamp embodiments. The strip 60 has abottom reflective layer 62, a bottom substrate 64, and a top substrate66. The substrates 64 and 66 may be transparent flex circuits, which arecommercially available. The substrates 64 and 66 include metal traces 68that connect the bare LEDs 22 in series. In one embodiment, the LEDs 22are vertical LEDs, with a wire bond pad on a top surface and areflective electrode covering the entire bottom surface. By using thestrip structures described below, no wire bonding is needed. The strips20 may only be 1-2 mm thick and less than 5 mm wide so as to be veryflexible and easily affixed over a rounded bulb form. The strip 60 maybe expanded in length and width directions to include any number ofstrings of LEDs and strings of any number of LEDs.

FIG. 9B is a perspective view of an alternative form of an LED strip 69that may also be used as the strips 20 in embodiments where electricalcontacts are desired to be made at only one end of the strip. Trace 68interconnects the LEDs and can be configured to provide a return path tothe same end of the strip as the input trace.

FIG. 10A is a cross-sectional view of four LEDs 22 in the strip 60sandwiched between substrates 64 and 66. Metal traces 68 on the topsubstrate 66 and metal traces 70 on the bottom substrate 64 overlap andelectrically connect during a lamination process to seal the LEDs 22between the substrates 64 and 66 to create a series connection. Aconductive adhesive may be used to electrically connect the anode andcathode electrodes of the LEDs 22 to the traces and to electricallyconnect the overlapping traces together.

FIG. 10B is a magnified top down view of two LED areas in the strip 60of FIG. 10A. The traces 68 and 70 overlap when the substrates 64 and 66are laminated to form a series connection.

In one embodiment, there may be 12 LEDs in series in a single strip todrop about 40 volts. Ten to fifty or more strips can be connected inparallel (e.g., to the same power supply terminals or to separatecurrent sources) to generate any amount of light.

The LEDs 22 in FIG. 10A may emit a blue light, which is converted towhite light by a YAG phosphor or red and green phosphors, or other lightconverting materials known in the art, overlying the LEDs 22 orpositioned remotely from the LEDs 22. Surrounding a blue LED with awhite light phosphor is well known, where blue light leaking through thephosphor layer combines with the yellow light or red and green lightproduced by the phosphor to create white light. It is also well known toprovide a remote phosphor tile over the LED. For example, the spacearound the LEDs 22 in FIG. 10A is filled with a phosphor contained in asilicone binder, and a phosphor tile is affixed on the top substrate 66overlying each LED 22 so that each LED area emits white light 70 havingany color temperature or color coordinate.

FIG. 11A illustrates an end of the LED strip 60 where a terminal pad 74is formed on a portion of the bottom substrate 64 that extends past thetop substrate 66. Since the terminal pad 74 is electrically connected tothe anode (bottom contact) of the end LED 22 in the strip 60, theterminal pad 74 will be connected to a terminal of the current source 46(FIG. 4), which may be a terminal on the power supply module. FIG. 11Bis a top down view of the end of the strip 60. A similar termination isat the other end of the strip 60 where the strip terminal pad isconnected to a cathode of the end LED 22 and connected to the pad 24(FIG. 2) that provides the positive voltage to the strips 60.

FIG. 12 illustrates a portion of a different type of strip 80, where thebottom substrate 82 includes traces 84 which connect the bottomelectrodes of the LEDs 22 to a metal slug 86, or other metal via, andthe top substrate 88 includes traces 90 that connect the LEDs 22 inseries when the substrates 82 and 88 are laminated together. Phosphor 94surrounds the LEDs 22, and a phosphor tile 96 overlies the blue LEDs 22to create white light.

In another embodiment, the slug 86 can instead be a conductive elementwith fusible properties or other useful electrical properties, such asany one of, or combinations of, surge protection, switchability, or evendigital memory storage, current control, or filtering. Therefore, theconnections between LEDs may be managed or even selectively opened orclosed after initial fabrication by laser, overcurrents, etc.

LEDs other than blue LEDs may be used, such as UV LEDs. Suitablephosphors and other light conversion materials used separately or inmixtures are used to create white light or various desirable colorpoints as may be necessitated by the system. Instead of LEDs, any otherlight emitting dies can be used, including laser diodes. OLEDs and otheremerging light generating devices may also be used. Instead ofphosphors, quantum dots or other wavelength conversion materials may beused.

Further descriptions of suitable flexible LED strips and sheets arefound in U.S. patent application Ser. No. 12/917,319, filed 1 Nov. 2010,entitled Bidirectional Light Sheet for General Illumination, assigned tothe present assignee and incorporated herein by reference.

In all embodiments, depending on the desired light emission, the LEDstrips or LED sheets may be bidirectional, meaning that light is emittedfrom both surfaces of the strip or sheet. FIGS. 13-15 illustrate somesuitable bidirectional light strip/sheet structures, where more detailmay be found in the above-mentioned U.S. patent application Ser. No.12/917,319.

FIG. 13 illustrates LED dies 100 that are oppositely mounted in a lightstrip or sheet to create a bidirectional emission pattern. There is noreflector layer covering the bottom of the strip/sheet. Any number ofLED dies 100 are connected in series by alternating the orientation ofthe LED dies along the light strip/sheet to connect the anode of one LEDdie to the cathode of an adjacent LED die using metal conductors 102 and104 formed on the top substrate 106 and bottom substrate 108. Thesubstrate electrodes contacting the LED electrodes 110, formed on thelight-emitting surface of the LED dies, may be transparent electrodes114 such as ITO (indium-doped tin oxide) or ATO (antimony-doped tinoxide) layers. Alternatively, very thin conductive traces that are nottransparent may be used that may only occlude a small percentage of thelight emission from the LED die. A phosphor layer 116 may be depositedto generate white light from the blue LED emission. The sides of the LEDdies 100 may be encapsulated by phosphor 118 infused in a siliconebinder.

FIG. 14 illustrates two light strips/sheets back-to-back. The LED dies120 are shown as flip-chips, and the conductor layers forinterconnecting the LED dies on each side in series are deposited onopposite sides of the middle substrate 122. The light strip/sheetstructure is sandwiched between transparent substrates 124 and 126. Themiddle substrate 122 may include a reflective layer that reflects allimpinging light back through the two opposite surfaces of thebidirectional light strip/sheet.

FIG. 15 is another example of two light strips/sheets, similar to thelight sheet described with respect to FIG. 10A, affixed back-to-backwith a middle reflective layer 130. The conductors 68 and 70 andsubstrates 64 and 66 are described with respect to FIGS. 10A and 10B.The light strips/sheets may be affixed to the middle reflective layer130 using a thin layer of thermally conductive silicone or otherthermally conductive adhesive. Phosphor 132 may be used to convert theblue LED light to white light. The substrates 66 may be formed withlenses 136 to create the desired light emission.

The middle reflective layer 130 may be a good conductor of thermalenergy, which can assist the conductors 68 and 70 in dissipating theheat from the LED dies 22. There may be enough thermal mass within thelayer 130 that it provides all of the heat sink required to operate theLED dies 22 safely or it may be extended laterally, beyond the edges ofthe substrates 64 and 66, to regions where the heat may be dissipatedmore freely to the air within the lighting fixture or lamp. Reflectivelayer 130 may also interface to matching thermal details within theluminaire to extend the thermal conductivity to other surfaces.

The light output surfaces of the various substrates may be molded tohave lenses, such as Fresnel lenses, that customize the light emissionpattern. Different lenses may be formed over different LED dies toprecisely control the light emission so as to create any spread of lightwith selectable peak intensity angle(s).

Any of the lamps described herein may use any of the light strips/sheetdescribed herein to achieve a desired light emission pattern or toachieve the desired lumens output.

FIG. 16 is a front view of a light sheet 138 containing manyencapsulated bare LED dies 140. For example, there may be 100-200 LEDsin the light sheet for emulating a 60 watt incandescent bulb. The lightsheet 138 may be bidirectional or emit from only one side. In oneembodiment, the LED dies 140 in a single column are connected in series,and the columns are connected to individual current sources in the powersupply module within the lamp. The LED light is phosphor-converted toproduce white light of a certain color temperature.

FIG. 17 illustrates the light sheet 138 of FIG. 16 bent in a cylinder asa replacement for an incandescent bulb. If the general size of the bulbis to be maintained, the diameter of the cylinder may be on the order of2.5 inches and the height of the cylinder may be on the order of 2-3inches. The standard Edison screw-in connector 146 is shown.

FIG. 18 illustrates a light sheet 148, similar to FIG. 16 but formedcircular, where the light sheet 148 is bent to form a cone or truncatedcone as a replacement for an incandescent bulb (the top of the truncatedcone is indicated by a dashed line). The light emission may be only up,only down, or bidirectional. In another embodiment, openings 149 areformed in the sheet 148 for air to flow through.

FIG. 19 illustrates a plurality of LED strips 154 around a transparentcylindrical form 156. The strips 154 are shown overlapping and spiralingfor better mixing of light from the individual strips 154. The ends ofthe strips 154 are connected to the positive voltage terminal andcurrent source terminals of the driver module in the base of the lamp.

An alternative embodiment could have the strips woven to create a lampform and provide structural integrity. Since the strips are transparent,they will still allow light to pass through and not create losses due toshadowing.

Blue LED dies have slight variations in peak wavelength due to processvariations. However, when the phosphor-converted light from a variety ofLED dies are combined, their observed correlated color temperaturealong, or proximate to, the well-known black body curve is generally theaverage of all the individual color temperatures. Therefore, for allembodiments, the color temperature, or color coordinates, or spectralpower distribution (SPD) of each LED strip may be measured byconventional optical test equipment when energizing the strip, and thestrips are binned (e.g., classified in a memory or physically separatedout) based on color temperature, or color coordinates, or SPD. In somecases, an SPD has an equivalent correlated color temperature. The binsmay be separated by, for example, 10K or 100K temperature resolutions orany other resolution, depending on the desired color temperatureprecision. When the strips are to be combined into a single lamp, thestrips from different bins may be combined to achieve the target colortemperature, or color coordinates, or SPD, assuming the light isgenerally on the Planckian locus. A simple algorithm for mixing colortemperatures or SPDs to achieve the target color temperature or SPD maybe used by a computer simulation program to determine the number ofstrips from the various bins to combine to generate the target colortemperature or SPD. The algorithm may also determine the placement ofthe strips relative to each other on the form in order to achieve thetarget color temperature or SPD 360 degrees around the lamp. In thisway, the yield is very high since all strips would be used irrespectiveof its color temperature or SPD. Such mixing of color temperatures,color coordinates, or SPDs may also be performed on an LED by LED basisto achieve a target overall color temperature, or color coordinate, orSPD per strip. In this way, lamps will be produced that outputapproximately the same color temperature. This is in contrast to a welldocumented trend in the industry towards utilizing fewer and fewer largeLED dies to achieve the target light flux. In this latter case therequirement for careful binning becomes increasingly important with anattendant yield issue that begins to increase the cost of manufacturing.

In one embodiment, the blue LEDs are tested and binned, such as in peakwavelength resolutions of 2 nm, and the specific combinations of LEDs ina strip are applied to an algorithm to determine the correlated colortemperature or SPD of the strip without the need for separately testingthe strip. Alternatively, the LEDs do not need to be tested separately,and the only color testing and binning are performed at the strip level.This greatly reduces testing and binning time.

Since a typical LED manufacturer bins the blue LEDs with a peakwavelength resolution of 2 nm and only uses LEDs from the same bin in asingle device for color uniformity, any technique to allow the use ofLEDs from different bins in a single device, even within a peakwavelength range of 4 nm, will greatly increase the effective yield ofthe LEDs. Therefore, using blue LEDs having peak wavelengths within a 4nm range or greater in the same strip is envisioned.

Generally, the LEDs that make up the strips have a certain range of SPDsthat occurs as a result of process variations and other limitations thatoccur during the fabrication process. It is a goal to use anycombination of such LEDs to maximize the LED yield and reduce the costof the resulting lamp.

One scenario may be that the LEDs in a single strip are from widelydiverse bins, separated by, for example, 10 nm. However, the wide SPD oflight from the single strip may desirably increase the color renderingindex (CRI) of the strip.

If the same combination of LEDs from different bins is used in eachstrip to create the desired target color temperature or SPD for eachstrip, testing each strip is unnecessary.

In another embodiment, each pair of adjacent strips is selected so thatthe aggregate SPD or color temperature of the pair approximately matchesthe SPD or color temperature of the lamp. This improves color uniformityaround the lamp and allows a wide range of LED bins to be used in thestrips. Any number of strips may be combined to generate the target SPDor color temperature.

The same principle applies as well to color converted strips that may beselected based upon their final binned performance and when combined inthe aggregate within a single lamp provides the target SPD and fluxperformance. These are then manufactured with a range of blue LEDdominant wavelengths, color converted by any one of a number of means,and then binned based on their final flux, SPD and/or othercharacteristic that permits a uniformity within tolerance for theaggregate light output of the lamp. The light from strips of slightlydifferent color temperatures (from difference bins) can also be combinedto produce an aggregate target color temperature and via variabledriving means, can be controlled by internal or external means to createa range of color temperature or even track a typical incandescent colortemperature and flux dimming profile. Combining different strips withcompensatory color temperatures is an effective means to reduce theoverall color temperature variation between lamps and to enableadditional functionality or emulation to the finished lamp.

In an alternative embodiment, the strips 154 could be placed parallel toone another, similar to FIG. 6 and evenly or unevenly spaced.

Further, since the strip substrates may both be transparent, strips maycompletely overlap each other to combine the colors and increase thelight output per area.

The flexibility of the LED strips allows the strips to be temporarily oreven permanently bent or compressed for storage, shipping, or use.

FIG. 20 illustrates a solid state lamp 170 formed by a corrugated LEDsheet or by a plurality of LED strips affixed to a compressible form174, so that the lamp may be compressed for storage. The lamp 170resembles a small Chinese lantern. An additional benefit of thecorrugated shape is that some LEDs are aimed upward and some LEDs areaimed downward, providing a substantially spherical light emission 176similar to a standard bulb. The user may expand the lamp 170 to avariety of lengths, where the light emission pattern varies with length.A shorter length provides more up-down light, while a longer lengthprovides more side light thus enabling different photometric intensityprofiles for use in different lighting fixture means.

FIG. 21A illustrates a solid state lamp 180 having a base 182 containingat least a portion of a driver, where the LED strips 184 retain theirshape when bent. The strips 184 may contain a thin copper or aluminumstrip for heat extraction that additionally retains its shape when bent.The lamp 180 may be packaged with the strips 184 unbent for minimumspace, and the user may bend the strips 184 in any shape to achieve adesired emission pattern. While the design may be considered useful fordecorative means it may also provide for minimized packaging volume andenable a wide range of different fixture photometric profiles that canadd efficiency, aesthetic advantages and variety for new light fixturedesigns. For example, the strips 184 may be bent in a bulb shape toemulate the emission pattern of a standard bulb. A virtually unlimitedarray of light emission patterns, including some highly decorativeversions, may be enabled by this embodiment. In another embodiment, itis also possible to have different color coordinates or colortemperatures which may be differentially aimed to create differentpatterns within a lamp shade or luminaire. It is even possible tocombine strips with lambertian emission patterns with strips that haveprescribed directional light emission within the same bulb to enablemultiple functions from the same lamp. For example, it is possible tohave some strips designed for side illumination and indirect lightingwithin sconce while other strips are “aimed” with optical control toprovide strong directional up or down light for increased taskillumination. The LED strip 69 of FIG. 9B may be used in the embodimentof FIG. 21A.

A clear outer shell may be used to protect the strips in the embodimentof FIG. 21 and allow the lamp to be handled by the user.

FIG. 21B is similar to FIG. 21A but the strips 185 are designed withvariable widths and distributions of LED dies. In this embodiment, theLED dies are arranged in patches at the tips of the strips 185 thatwiden into larger areas at their tips. One advantage of this is toincrease the light flux at the “light center” of the lamp, which moreclosely emulates a standard incandescent lamp. This embodiment alsoallows for the LED dies to be turned through larger angles to enableaiming of the tips of the strips 185 to enable some of the functionalitydescribed above.

FIG. 22 is similar to FIG. 21A, where the LED strips 184 are straight oraimable via rotation and angular displacement. The distribution of LEDchips may also be adapted to be higher or lower in regions.

In one embodiment, a reflector may partially surround the strips 184 toconfine the beam, similar to an MR-16 type bulb. In another embodiment,additional strips may be affixed to the outer surface of the reflectorto emit light in a downward direction relative to FIG. 21. In anotherembodiment, a diffuser may also completely, or partially surround thestrips 184 to soften the light distribution. In both cases, thereflector or diffuser described above may be removable and replaceableas an option that is sold with the base lamp 21 or 22 and supplied asdirected or desired by the user or fixture design.

In FIGS. 21A, 21B, and 22, there may be two or more strips. In oneembodiment, there are up to 12 strips, each strip containing 12 LEDs inseries for providing sufficient lumens to replace a 60 watt incandescentbulb. The strips may be connected in parallel, and each strip may beassociated with its own current source in the power converter.

The strips may be corrugated instead of flat to create a broader beam.The strips may have lenses formed in them.

In one embodiment, the strips are about 1-6 inches long depending on theallowable space and desired light output. The strips may bendablebetween an angle perpendicular to the central axis of the lamp andparallel to the central axis to maximize control of the light emissionpattern. The strips may be arranged to emulate most types of standardbulbs. Any electrical connector can be used.

FIG. 23A illustrates a solid state lamp 188 formed of a single LED sheetor a plurality of LED strips, where the sheet or strips are configuredto create a polygonal cross-section. The sheet or strips may be affixedto a polygon form with flat sides. The polygon may be vented or madefrom thermally conducting material such that heat is transferred toother regions of the lamp for cooling. For example, ventilation holes189 in the base can result in buoyancy driven air flow to run parallelto the vertical axis within the lamp body and be ventilated in eitherdirection depending upon the orientation of the lamp.

FIG. 23B is a cross-sectional view of FIG. 23A along line A-A in FIG.23A showing that the lamp is a six-sided polygon to provide good 360degree light emission. Each side may be associated with its own currentsource to ensure substantially equal light output per side.

FIG. 24 illustrates a solid state lamp 188, similar to FIG. 23A, with asubstantially spherical diffuser 190 being positioned over it so thatthe light emission better emulates a bulb. The diffuser 190 alsoprovides protection for the LEDs and allows the user to apply torque tothe screw-in base without touching the LED strips. The diffuser 190 maybe held in place by a screw 192, a clamp, locking tabs, an adhesive, orany other means.

In another embodiment of FIG. 24, the diffuser 190 is designed to beadjustable up and down such that it can be positioned vertically atdifferent heights to effect a change in spatial distribution. Thediffuser 190 may also incorporate regions of diffusion with regions oftransparency with regions of specular reflectivity as may offer a uniquelight distribution for particular lighting fixture design. One suchexample in the incandescent world is to create regions near the tophemisphere of the bulb glass envelope with highly specular reflectivityto shield direct view of the filament. The equivalent property could beexploited in this design with the added advantage that it could bedesigned such that it could be adjusted vertically to control thecut-off angle suiting the user's requirements. Diffuser 190 may alsohave perforations 197 or reveals to permit air flow to pass from thebottom to the top for additional cooling of the LED dies. The screwfastener 192 shown is one example of a means to fix the diffuser to thecentral lamp structure. Other methods include snap fitting, threadedfitting and interference fitting that will provide for mechanicaljoining of the removable and replaceable reflector or diffuser assembly.

In another embodiment, diffuser 190 may contain a remote phosphor orlight conversion material to help create light of a desired spectrumfrom the underlying LED dies.

In one embodiment, there is no phosphor on the LED strips, so the stripsemit blue light. The diffuser 190 is coated with phosphor for convertingthe blue light to white light.

FIG. 25 illustrates a solid state lamp 188, similar to FIG. 23A, with ahemispherical or parabolic reflector 196 surrounding the LEDs.Optionally, perforations 197 in one or both of the reflector 196 or thediffuser/optic 202 will aid in cooling of the LED die. A variety oftypes of diffusers or reflectors may fit over the same lamp 188 toachieve different emission patterns. The light emission 200 from theLEDs 140 is shown reflecting off the reflector's 196 inner surface andbeing emitted in a forward direction to achieve a spotlight effect. Atransparent or diffusing window 202 may be provided over the lamp. Thereflector 196 may instead be a diffuser and can be designed to beremovably attached to the lamp pedestal such that the end user maychange the desired distribution from a hemispherical light distribution,as with a globe diffuser, to a reflector lamp with a narrow beamdistribution by changing the reflector 196. Preferably, there will be anallowance for mechanically connecting the reflector/diffuser componentand any external lenses, diffusers or homogenizers as are known in theart. The wide variety of optical conversion materials and structuresthat can be attached to the central lamp form offers end users greatutility in that they can readily modify the lamp spatial emissioncharacteristics without removing the underlying lamp from the socket.Since the underlying lamp form 188 can remain in a luminaire socket fordecades of useful life in residential and commercial applications it isadvantageous and environmentally prudent to be able to readily changethe optical and emission characteristics of the lamps over time.

Additionally, the LED strips or LED sheet in FIG. 25 may be replaceablewhile retaining the remainder of the lamp to achieve differentcharacteristics, such as increasing or decreasing the lumen output orchanging the color. The LED strip or sheet may have a plug-in connectorand be a snap-fit.

The bottom portion of the lamp 188 may be formed of a good thermalconductor and is exposed to ambient air with air channels for aiding incooling. In this way, the lamp is cooled in any orientation.

FIG. 26A illustrates a solid state lamp 210 having a plurality of LEDstrips 212 supported at their ends to form a lamp having a customizableshape. The strips 212 may have an increased density of LEDs 214 neartheir middle to provide more uniform spherical light emission. Theradius of curvature of the strips 212 may be set with a screw 216 at thetop of the lamp 210 connected to the base 218. The screw 216 (or otherfastener) may also be adapted to be gripped by a user to provide atorque for screwing the lamp into a socket. A positive voltage iscoupled to one end of the strips 212 and current sources are connectedto the other ends of the strips 212, as shown in FIG. 4.

In another embodiment, all connections to the power converter can bemade exclusively at the bottom of the strips so that the top of the lampmay be electrically neutral for safety.

In another embodiment, FIG. 26A may have the strips 212 rotationallyvariable such that all of the strips can be fanned to one side ordistributed evenly. For example, FIG. 26B may also represent a flat,fanned out array of strips 212 with all electrical connections at oneend near the central pivot point. This mode can be useful for uses ofthe lamp where it may be desirable to have the light emit from only oneside of the lamp such as in a wall sconce.

In another embodiment, the strips 212 may be selectively fanned out bythe user in the bent configuration shown in FIG. 26A so that the lampemits light in an asymmetrical pattern.

FIG. 26B is a top down view of FIG. 26A showing the individual strips212 and the screw 216.

FIG. 27 illustrates a solid state lamp 230 that is compressible forpackaging. The LED strips 232 are diamond shaped, or any otherconvenient foldable shape, to provide an increased density of LEDs nearthe middle of the strips for more uniform spherical light emission. Thestrips 232 are formed to have a crease in the middle, or separate strips232 may be provided on the upper and lower halves of the lamp 230 toavoid a severe bend in the strips. The LED driver may be within the basestructure 234.

As with FIG. 20, the height of the lamp 230 may be adjustable to greatlycontrol the light emission pattern. A more compressed lamp will providemore up-down light, while and expanded lamp will provide more sidelight. The height may be adjustable by turning a central screw or simplycompressing or expanding a central friction slip rod or any other means.

The lamps of FIGS. 20 and 27 may have a large surface area for bettercooling of the LEDs. The central open area further increases aircooling.

In one embodiment, a sheer insect-blocking netting is provided over theopening.

An Edison-type screw-in connector for an incandescent bulb is usuallyrequired to provide a portion of the support for the vacuum chamber forthe filament. However, for a solid state lamp, the electrical connectorcan be any of a variety of shapes as long as it has the ability toconnect to the standard Edison socket and provide the necessary safetyclearance for shock. In one embodiment, the lamp 230 has a screw-in typeelectrical connector 236, having a relatively narrow central shaft 237and two or more metal tabs 238 that engage the threads in the Edisonsocket 239 (threads and hot electrode shown). The connector's 236 hotelectrode 240 is connected to a wire that runs inside the shaft 237 tothe driver.

FIG. 28 is a bisected view of the lamp 230 of FIG. 27 in its compressedstate, showing the electrical connector 236 in its stored state. Theconnector 236 is relatively thin and may be foldable for storage.

FIG. 29A illustrates in more detail the connector 236 of FIG. 28. Theconnector 236 has wide flat sides 246 and portions of threads 248 on itsnarrower sides that correspond to the matching screw shell of thestandard socket 239. The view of FIG. 27 shows the narrow side of theconnector 236. The threaded area may be copper affixed to an insulatingsupport material 249 (FIG. 29A). The structure will screw into astandard Edison socket 239. A hot electrode 240, extending through theinsulating support material 249, connects to a top terminal 250, whichis, in turn, connected to one input of the driver. The driver isoptionally housed within the base structure 234, which also provides afinger safe shock shield over the top of the corresponding socket. Thecopper threads 248 connect to another input of the driver. Tabs 238extend from the connector 236 in its down position once the connector236 is positioned by the user. The tabs 238 can be provided on bothsides of the connector 236 and, when locked in position, provides fourpoints of contact within the Edison socket 239 and permits the lamp tobe screwed into the socket in a normal fashion. Since solid state lightsources offer extraordinary life expectancy measured in decades, it isreasonable that lamps will typically be installed and then left for manyyears without any need for replacement. Thus, the requirement for simpleremoval and replacement may be relaxed in terms of mechanicalconvenience and ergonomics and instead be directed to quick installationmethods for rapid deployment in the field.

In another embodiment, which may be similar in appearance to FIG. 27,the metal tabs 238 act as resilient metal springs that allow the lamp230 to just be pushed into the Edison socket 239 without any turning ofthe lamp. The tabs 238 have an acute angle portion that engages thethreads of the socket 239 and resiliently locks in the lamp. There maybe 2, 3, or four tabs 238, depending on the desired rigidity of the lampconnection to the socket. The hot electrode 240 may be spring loaded(urged into its expanded state) to ensure firm contact with the hotelectrode of the socket as the tabs 238 settle into a trough of thesocket thread. Typically, an Edison type screw-in socket has a resilienthot electrode 252 (FIG. 27), so spring loading the hot electrode 240 ofthe connector 236 may not be needed. A central support shaft may formthe central axis of the lamp and can be used to apply the pressure forinserting the connector 236 into the socket 239. In such a push-inembodiment, the copper threads 248 of FIG. 29A would be omitted, and thecentral shaft may be a more narrow cylinder or rectangular bar.

FIG. 29C is a cross-sectional view of another embodiment of a push-inconnector for an Edison-type screw-in socket. In FIG. 29C, conductivecaptive balls 251 within receptacles around a conductive or insulatingvertical shell 252 provide the mechanical locking within the Edison-typesocket. The captive balls 251 are urged outward by springs 253 so as tohave sufficient restorative force that they can readily be inserted withsufficient pushing force and yet remain tight within the socket formechanical and electrical integrity. Removal is the reverse and could beeither by exerting a strong pull or via the typical unscrewingrotational action of traditional designs. The neutral or groundpotential of the socket is conducted by the balls 251, springs 253, andcentral metal conductor 254 to a power supply input of the LED driver(not shown) in the base of the lamp. The hot potential is conducted fromthe hot electrode 255 by a wire 257 to the other input of the driver.Many different ways of coupling the potentials to the driver areenvisioned.

In another embodiment related to FIG. 29C, the act of pushing verticallydown on the top of the lamp will force a spring loaded central plunger(may be similar to the conductor 254) down and free the balls 251 withintheir receptacles in a horizontal direction, allowing the lamp to befreely inserted. As the plunger is allowed to move to its normal restingposition, a central cam may push the balls out and lock them into thesocket. Removal will then either be via a standard rotational motion orcould be enabled by having a reverse detail on the central shaft thatwill permit the balls 251 to be retracted when the lamp is pulled fromthe socket.

FIG. 30 illustrates an electrical connector 256, extending from a base258, having a handle 262 affixed to it to provide torque for screwing asolid state lamp into a socket or pushing the lamp into the socket. Thehandle 262 is optional if there is other means to screw or push the lampinto the socket. The base 258 may support the LED strips or a bulb form.

In certain applications, it is desirable for a solid state lamp toprovide a more directed light emission rather than a standard bulbemission. FIGS. 31-33 illustrate a solid state lamp that may be used toprovide a more directed beam.

FIG. 31 is a side view of a solid state lamp 268 that has a directedlight emission. The lamp 268 has a standard screw-in base 14, and adriver is included in the lamp 268. The lamp 268 has a body 270 forsupporting a plurality of LED strips, which may be any of those LEDstrips previously described. A diffuser 272 is optional.

FIG. 32 is a top down view of the lamp of FIG. 31 without the diffuser272. In the example, there are eight LED strips 274 encapsulating anynumber of bare LED dies 276. There may be any number of strips and anynumber of LED dies per strip, such as 12 strips, each containing 12 LEDdies connected in series.

A central pad 280 is connected to an end lead of each strip 274 and maysupply a positive voltage provided by the driver. The other end of eachstrip 274 may be connected to a common conductor or to an associatedcurrent source, as shown in FIG. 4. In the simplified example of FIG.32, the perimeter of the circle is a common conductor 282 connected toall the strips 274 so all the strips 274 are connected in parallel.

If the surface 277 supporting the strips 274 is flat, the light emissionfrom the strips 274 will, at most, be hemispherical, and lenses formedon the strips' substrates may be used to narrow or direct the beam tocreate a spotlight effect. The diffuser 272 may instead include a lensfor directing the beam. The lamp 268 may replace directional lamps suchas types MR-16 (2 inch diameter), R30 (3¾ inch diameter), PAR 38 (4¾inch diameter), and others.

The surface 277 supporting the strips 274 may be thermally conductiveand reflective, such as aluminum, to draw heat from the LED dies 276,and the body 270 removes the heat from the metal by transferring theheat to the ambient air. Holes may be formed in the body 270 to createan air flow contacting the bottom surface of the metal support. If theLED dies 276 are low current types (e.g., 20 mA), removing heat will notbe difficult since the LED dies 276 are spread over a relatively largearea.

The surface 277 supporting the strips 274 need not be flat, but may beconcave or convex (e.g., conical) to affect the light emission pattern,such as making the light beam wider or narrower, or increasing theproportion of side light, etc.

FIG. 33 is a top down view of the lamp of FIG. 31 where each LED strip286 has a curved shape to better distribute the LED dies 276 over themetal surface 277. This not only creates a more uniform light beam butspreads the heat from the LED dies 276 over a larger area for increasedcooling.

Many other shapes of the LED strips can be used. In another embodiment,a single strip can be formed in a long spiral around the central axis todistribute the LEDs. In another embodiment, the strips may be concentriccircles. Instead of LED strips, the LEDs may be distributed in an LEDsheet, such as shown in FIG. 16.

As previously discussed with respect to FIG. 19, the strips 274/286 maybe pre-tested for color temperature and binned, and strips may becombined from different bins to create a target color temperature.Therefore, all lamps 268 will output white light having the same overallcolor temperature.

The flexible structure and selectable width of the light strips allowsthem to be bent to form various types of lamps having particular lightemission characteristics.

FIG. 34A illustrates a light strip 300 mounted on a curved metal backingthat can be rolled up similar to a conventional metal tape measure. Themetal may be the same steel as used in a tape measure or any planarmaterial with the ability to spring into shape. FIG. 34B is a side viewof the light strip 300 rolled up. The metal backing provides strength tothe strip 300 when it is unrolled, due to its U-shape, so the strip canbe self supported up to 8 feet. The light emission 302 may be broad dueto the curved shape of the light strip 300. Electrodes 304 project fromthe strip 300 and may connect to a standard fluorescent bulb socket. Ametal backing is not necessary, and other material may be used, such asplastic. If the light strip is suitably formed, no backing material maybe necessary.

The light strip 300 may be a lamp for installing in a fixture or may bethe complete fixture itself. As a complete fixture, the light strip maybe any width, such as up to one foot wide or wider, to beself-supporting. For the light strip 300 to be a fixture in itself, theelectrodes 304 are attach to end caps, which are supported by wiresconnected to a ceiling or supported by a T-bar grid. The supportingwires carry the current, or separate wires carry the current. The strip300 may be arced up or down, depending on the desired lightdistribution.

It is estimated, that the light strip 300 may be self-supporting up to12-16 feet if it has sufficient width. LEDs may be mounted on both sidesof the strip to provide bidirectional lighting where the ceiling is alsoilluminated. This invention greatly reduces the packaging and volumeinherent in the shipping of typical planar light sources since it isreadily rolled up and delivered to site in a compact fashion savingsignificantly in packaging and delivery costs. The use of raw materialsis also significantly enhanced as far less mass is consumed by thisstructure to provide a given amount and distribution of lighting withinthe space.

In another embodiment, the U-shape is inverted, and the LEDs may bemounted on both sides if the strip.

In another embodiment, the U shape is joined back to back with another Ushape such that the cross section is a free-form sprung “eyeball” typeshape.

In another embodiment, the strip 300 does not have to be rollable, butmay be stackable for storage. This greatly simplifies the constructionof the strip 300 since it may be formed as a rigid piece. The strip 300may only have one electrode 304 per end, or have both electrodes 304 atonly one end.

FIG. 35 is a perspective view of a cylindrical lamp 306 formed ofvarious sections 308, 309, 310 of light sheets, where each light sheetcontains an array of LEDs and bent to form a cylinder. The lamp 306telescopes due to the sections 309 and 310 having progressively smallerdiameters. The electrodes for each section are connected by wires 312 tothe lamp electrodes 314. Other means of electrical conduction may beused. Electrodes may be at both ends of the lamp 306. The lamp 306 maybe fully extended or partially extended. If partially extended, lightfrom an inner light sheet will emit through the outer light sheet sincethe light sheets may be transparent. In one embodiment, there are foursections of about one foot each to replace a four foot fluorescent bulb.The lamp 306 may be used to replace a variety of lamp lengths andwattages, such as 2, 3, or 4 foot lamps.

FIG. 36 illustrates a lamp 318 that is formed of a single spiral lightstrip 320 that is stretched into its fully expanded position shown inFIG. 36. The edges of the light sheet are shown forming a helix. Thespiral may effectively lock in place by tabs or other means. Forexample, if one edge of the spiral strip has a U-shaped edge thatcorresponds to the thickness of the other side of the strip then it willnaturally snap back into the U channel as the spiral is unfurled. Oncesnapped back the spiral will effectively be a rigid tube similar to acardboard spiral tube used as a mandrel for winding paper. Electrodes(not shown) may protrude from one or both ends.

FIG. 37A illustrates a lamp formed of a light sheet 322 bent into acylinder, where the LEDs' light emitting surfaces are facing into thecylinder. The outer surface may be reflective so all light 324 isemitted from the open ends of the cylinder. One end may be blocked by areflective plate. The colors emitted by the LEDs are highly mixed sothat the light exiting the lamp is very uniform. Such a lamp may beaffixed to a wall to provide accent lighting or provide directedlighting onto a surface.

FIG. 37B illustrates a lamp similar to that of FIG. 37A, where the lightsheet 326 is bent to form a truncated cone facing up or down. The light328 is emitted through the large open end, and there is less reflectionof the light before exiting compared to the embodiment of FIG. 37A. Thebottom may be open or provided with a reflector.

FIG. 38 illustrates three overlapping light sheets/strips 330, 331, 332,each sheet/strip encapsulating an array of LEDs 334. All LEDs 334 emitlight 336 in the same direction. The substrates are all transparent soas to transmit the light. Therefore, the light output per area of a lampmay be increased using this technique. Any number of sheets/strips mayoverlap.

The overlapping sheets/strips 330-332 may be used in any of theembodiments described herein.

In another embodiment, the three sheets/strips 330-332 may be connectedto different power converter terminals. In a low light state, only onelight sheet/strip (or only one set of strips) may be energized. Inhigher light states, the additional strips or sheets would be energized.A three-way fixture switch or other control means may be controlled bythe user to apply power to the redundant strips or sheets to emulate athree-way bulb. The electrical connector for the lamp may be a standardthree-way bulb connector. A mixture of strips and a sheet may also beused. In an another embodiment, the strips may be of different spectralpower distributions and be independently controlled or dependentlycontrolled by known means to provide a composite spectral powerdistribution. Open loop or closed loop electrical control means mayprovide for a variety of color temperatures or color points to bereproduced by the assembly of overlapping sheets/strips.

FIG. 39 illustrates that the substrates used to form a light sheet 338may be stretchable so as to conform to 3-dimensional objects, such as ashallow dome 340. The LEDs in the sheet 338 may emit light in eitherdirection. The stretchable substrate may have an adhesive surface tostick to the form.

To maintain a certain brightness level over very long periods, redundantstrips may be used, as shown in FIG. 40. FIG. 40 illustrates a set ofactive strips 350 containing LEDs 352 and one or more redundant strips354. The active strips 350 are normally all energized. The redundantstrips 354 would not be energized until an open circuit detector 356detects that a normally operational strip has either become an opencircuit or has otherwise failed. Then the detector 356 controls acurrent source 358, via a switch 360, to power up a redundant strip 354.Many other types of circuits may be used to detect a non-operationalstrip and, in turn, energize a redundant strip. A redundant strip 354may also be energized in response to an active feedback sensor sensingthat the light has dropped below a threshold level.

In another embodiment of FIG. 40, the strips may be enabled to selfregulate system output by utilizing control means responsive totemperature or light flux that enable warmer strips to dim and forcooler strips to brighten such that overall efficacy and longevity ismaximized. For example, the strips may be cooled by reducing a PWM dutycycle of the strips.

In another embodiment of FIG. 40, parallel strips 354 of LEDs producedwith approximately equal impedance are powered and wired such that achange in the impedance of each strip is detected by the detector 356.This detection can be by monitoring the currents through the strips 354and detecting any increase in current due to a drop in resistance of aparticular LED, such as the lowering of an LED's voltage drop due toexcess heat. The average current through this decreased resistance canbe reduced by the detector 356 decreasing the duty cycle of theindividual LED or the strip 354 which contains it. As the decreased LEDor strip 354 cools, the other, parallel strips will be radiatingsufficient light to keep the integrated flux constant. As other LEDsheat and drop their resistance and have their duty cycle decreased inturn by detector 356, the previously reduced strips will have cooled andtheir duty cycle can now be increased so that the integrated light fluxremains the same. Accordingly, each strip will have its resistancemonitored and current adjusted such that it cools while other parallelstrips are radiating. The current can be controlled by controlling aresistance, voltage, or any other suitable parameter. This control oftemperature and current through the various junctions can be arranged sothat the required light flux is maintained but the degradation of thevarious junctions is reduced, thereby extending the life.

Accordingly, there can be no thermal runaway problems and the lifetimeof each strip will be approximately the same.

The continual detection and control of each strip 354, controlled bydetector 356, allows a feedback and control loop to occur that

i) detects overheating junctions through their drop in resistance;

ii) cools the overheating junctions by reducing their duty cycle;

iii) transfers the extra load to other strips operating with normalresistance;

iv) keeps constant the overall flux of light from the entire lightsheet, luminaire, or device, either through statistics or through anactive larger-scale control loop;

v) allows the entire device to have a substantially longer lifetimethrough the lengthened lifetimes of the component LEDs and LED lightstrips.

The various features of the lamps described herein may be combined inany way.

The inventions can be applied to any form of lamp having any type ofelectrical connector. The lamps may run off the mains voltage or abattery. If a battery is the power supply, the selection of the numberof LEDs in a strip (determining the voltage drop) may be such that thereis no power supply needed in the lamp.

Having described the invention in detail, those skilled in the art willappreciate that given the present disclosure, modifications may be madeto the invention without departing from the spirit and inventiveconcepts described herein. Therefore, it is not intended that the scopeof the invention be limited to the specific embodiments illustrated anddescribed.

What is claimed is:
 1. A solid state lamp comprising: a base connector configured to electrically connect the solid state lamp to a power source, the base connector defining an axis; and a bulb portion extending along the axis and attached to the base connector, the bulb portion comprising a strip, the strip comprising: an elongate substrate extending from a first end to a second end opposite the first end; a plurality of spaced-apart light-emitting diode (LED) unpackaged dies; electrical connectors configured to provide power to the LED unpackaged dies; and an encapsulant encapsulating the LED unpackaged dies on the substrate, wherein the substrate comprises a reflective material.
 2. The solid state lamp of claim 1, wherein each of the LED unpackaged dies has a first surface configured to reflect light from within the LED unpackaged die, the first surface facing the substrate.
 3. The solid state lamp of claim 1, wherein the encapsulant comprises a phosphor and a binder.
 4. The solid state lamp of claim 3, wherein the binder comprises a silicone.
 5. The solid state lamp of claim 1, wherein the elongate substrate comprises a dielectric reflective material.
 6. The solid state lamp of claim 1, wherein the elongate substrate comprises a polymer, a glass, or a metal.
 7. The solid state lamp of claim 1, wherein the elongate substrate is a straight elongate substrate.
 8. The solid state lamp of claim 1, wherein the elongate substrate is a curved elongate substrate.
 9. The solid state lamp of claim 8, wherein the curved elongate substrate is a flexible curved substrate.
 10. The solid state lamp of claim 8, wherein a projection of the strip onto a plane defines a curved path.
 11. The solid state lamp of claim 1, further comprising a support structure, wherein the strip is supported by the support structure.
 12. The solid state lamp of claim 11, wherein the support structure comprises wires.
 13. The solid state lamp of claim 11, wherein the strip is coupled to the support structure at at least one end of the strip.
 14. The solid state lamp of claim 11, wherein the support structure comprises a rod.
 15. The solid state lamp of claim 11, wherein the support structure maintains a curved shape of the strip.
 16. The solid state lamp of claim 11, wherein the electrical connectors comprise terminals coupled to the support structure.
 17. The solid state lamp of claim 1, wherein the substrate has a width of less than 5 mm and a thickness of less than 2 mm.
 18. The solid state lamp of claim 1, further comprising one or more additional strips each comprising an elongate substrate extending from a corresponding first end to a corresponding second end opposite said first end, each elongate substrate supporting a corresponding plurality of spaced-apart LED unpackaged dies encapsulated on the elongate substrate.
 19. The solid state lamp of claim 18, wherein the strips are symmetrically distributed around the axis.
 20. The solid state lamp of claim 18, wherein at least one of the additional elongate substrates of the one or more additional strips are straight.
 21. The solid state lamp of claim 20, wherein at least two of the strips are non-parallel to each other.
 22. The solid state lamp of claim 20, wherein at least some of the strips are parallel to each other.
 23. The solid state lamp of claim 1, wherein a radial distance between the strip and the axis varies along the axis.
 24. The solid state lamp of claim 23, wherein the radial distance increases closer to the base connector.
 25. The solid state lamp of claim 1, wherein the strip is arranged in the form of a spiral or a helix.
 26. The solid state lamp of claim 1, wherein the LED dies are operatively interconnected without wire bonds.
 27. The solid state lamp of claim 1, wherein the LED unpackaged dies are flip-chip LED dies that are operatively connected via traces.
 28. The solid state lamp of claim 1, wherein the LED unpackaged dies are arranged between some of the electrical connectors and the substrate.
 29. The solid state lamp of claim 1, wherein the LED unpackaged dies are uniformly arranged in a row along the elongate substrate.
 30. The solid state lamp of claim 1, wherein the elongate substrate, the LED unpackaged dies, and the encapsulant are configured to mimic the appearance of a filament in an incandescent light bulb during operation. 